Certain products elicit a similar physiological kick, tripping the noodle's reward circuitry. A DaimlerChrysler study in Ulm showed pictures of 66 different cars--22 sports cars, 22 sedans and 22 small cars--to a dozen men, with an average age of 31, as they lay in a scanner. Far more than the other models, sports cars excited areas of the brain associated with reward and reinforcement. Among the sports cars that generated the strongest brain responses: the Ferrari 360 Modena, the BMW Z8 and the upcoming Mercedes SLR.

It's not just that sports cars have a more pleasing shape, says Walter, the psychiatrist with the University Clinic of Ulm who was involved in the study. They trumpet the driver's wealth and social dominance. "A sports car is like a peacock's tail," says Walter, a Honda driver. "Why should a female peacock choose a mate with a very huge tail? Because if you are strong and successful as an animal, you can afford to invest energy in such a useless thing." In other words, as people have known since our Paleolithic forebears carved the first fertility goddesses, sex sells.

Soda has an interesting effect on our heads, too. A century after Coca-Cola took cocaine out of its flagship beverage, neuroscientists are learning that soft drinks still work like the illicit drug--as well as like fat, salt, sugar--on our brains. P. Read Montague, a neuroscientist at Baylor College of Medicine in Houston, has demonstrated that subjects' brains register a preference for Coke or Pepsi that correlates with the product they choose in blind taste tests. (His study is not funded by the cola giants.) The brain of "Subject P" on the monitor in the Human Neuroimaging Lab, for instance, shows he is a Pepsi lover. After he got 35 alternating, but unidentified, squirts of Pepsi and Coca-Cola through a pacifierlike device while he was in a scanner, blood flooded areas of his brain involved in reward and decision making, but primarily after doses of Pepsi. In the neural taste test of 40 subjects, Montague found that kind of response less powerful with Coke.

So why does Coke outsell Pepsi? It has to do with the power of branding. Researchers are starting to decode the neural signature for brand preference. Justine Meaux, a neuroscientist at the privately held BrightHouse Institute for Thought Sciences in Atlanta, says the medial prefrontal cortex is active when people behold images of things to which they are extremely attached.In a recent BrightHouse Institute study, 30 subjects were put in MRI scanners and viewed images of products, people and activities--rock climbing, President Bush, BMWs and the National Enquirer, among them. "Preference has measurable correlates in the brain; you can see it," says Meaux, whose company charges on average $250,000 for such a study.

If companies can calibrate changes in preferences over time, it may help them engineer more durable brand loyalty. "This stuff is objectively measurable, and there are differences we can use to help guide our decisions in how we market to people," Meaux says. "We can see how we can change our behavior so someone will want to align with us."

Orwellian? Don't worry about it, says Baylor's Montague: "Marketers are already in your underwear drawer." These worries have been around forever. In 1957 Vance Packard's sensationalist bestseller The Hidden Persuaders suggested that consumers might be susceptible to "subthreshold" stimulation, such as odors and sounds, that "are just out of the range of conscious awareness." In time the panic over subliminal advertising subsided. But now, sighs Harvard's Zaltman, "There are people who think we can insert ideas into people's thinking." Not so, he says. His brain research, which has attracted business from companies like Coca-Cola, Hallmark and Johnson & Johnson, is aimed at understanding consumer motivation.

Outside of places like North Korea, brainwashing doesn't hold much commercial appeal. But insights into decision making and emotions are ripe for exploitation. Take the prefrontal cortex, an area that plays a key role in levelheaded decision making and long-term goals. It takes years to develop and then starts to lose some of its swagger when we're in our late 50s. That means kids under 12 and older people are more susceptible to urges that come from the amygdala, the emotional hot button in our heads. It responds to threats, emotional communication and sexual imagery--some of the stuff we see or hear in ads and other marketing ploys. The cookies on the low shelf in the grocery store are aimed at the 5-year-old's amygdala; an investment scam is aimed at the amygdala of a retiree. "By understanding the development of the prefrontal cortex, companies can market things in different ways," says Jordan Grafman, chief of the Cognitive Neuroscience Section of the National Institute of Neurological Disorders & Stroke at the National Institutes of Health. "There may be certain combinations of pitches they can use to appeal to the amygdala and prefrontal cortex. Or, if they know the age range of people watching a TV show, they can change a commercial to target them in different ways."

The rational response to the injection of brain waves into Madison Avenue is that it will neither revolutionize marketing nor make us consumer slaves. It will, rather, yield incremental benefits. "The human brain is the most complicated thing in the universe," says John Van Horn, a research associate professor in psychology and brain sciences at Dartmouth College. "It would be arrogant to say we could stick someone in a machine and understand everything."

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